1. Technical Field
The present invention relates to a testing apparatus for evaluating qualities of a rod-shaped test piece such as a cigarette, and more particularly to a ventilation-characteristic measuring apparatus which is suited to measure ventilation characteristics of a test piece and which is simple in construction.
2. Related Arts
In order to evaluate qualities of a cigarette, testing is made on various items such as the weight, circumference and length of the cigarette, the hardness of a cigarette portion thereof, and ventilation characteristics of cigarette and filter portions of the cigarette. A typical cigarette testing apparatus comprises an apparatus for measuring ventilation characteristics of a test piece based on a flow rate of air entering into the test piece from the outside of a ventilation vessel when the ventilation vessel is evacuated.
As shown in FIG. 1, a ventilation-characteristic measuring apparatus of this kind comprises a cylindrical container 1 having its upper and lower ends formed with openings for permitting a test piece such as a filter cigarette C to pass therethrough, first, second and third test-piece supporting devices 3a, 3b and 3c, disposed to be spaced from one another in the axial direction of the cylindrical container and coaxially therewith, for elastically holding a cigarette by means of test-piece holding members, and a rotary valve 4 for selectively closing the lower end opening of the cylindrical container 1. In the following explanations, the first, second and third test-piece supporting devices are sometimes collectively denoted by reference numeral 3.
The first, second and third test-piece supporting devices 3a, 3b and 3c are arranged to hold a tip end portion of a filter plug section F of a cigarette C, a boundary portion between the filter section F and a shredded tobacco section T thereof, and a tip end portion of the tobacco section T (i.e., a lower end portion, an intermediate portion, and an upper end portion of the cigarette), respectively. When the lower end opening of the cylindrical container 1 is closed by the rotary valve 4, =the first, second and third test-piece supporting devices 3a, 3b and 3c cooperate with the cylindrical container 1 to define a first, second and third airtight chambers 2a, 2b and 2c.
In FIG. 1, reference numeral 5 denotes a guide through which a cigarette C supplied to the upper end opening of the cylindrical container 1 is introduced into a central part of the third test-piece supporting device 3c, and reference numeral 6 denotes a guide through which the cigarette C is introduced into a central part of the second test-piece supporting device 3b. A stopper 7 is disposed for forward and backward motions at a location below the first test-piece supporting device 3a. The cigarette C is brought in contact at its lower end with the stopper 7 which is moved forward in advance to a location beneath the first test-piece supporting device 3a, whereby the supporting position of the cigarette C by means of the first, second and third test-piece supporting devices 3a, 3b and 3c is determined.
As shown in Japanese provisional patent publication no. 63-259436, for instance, each of the test-piece supporting devices 3, having a peripheral face thereof formed with a threaded groove, is threadedly engaged with a threaded inner peripheral face of a flange-like mounting portion 1a which projects from an inner peripheral face of the cylindrical container 1 radially inwardly of the container, whereby the supporting device is mounted to the cylindrical container. The test-piece supporting device 3 is comprised of a ring-shaped holder 11 shown in FIGS. 2 and 3 and a test-piece holding member 12 made of an elastic material such as rubber and shown in FIGS. 2 and 4. The holder 11 has a ring-like recess 11a formed in a central part of an inner peripheral face of the holder so as to extend along the entire circumference of the inner peripheral face, and two O-ring holding grooves 11b which are formed in the inner peripheral face at locations above and below the recess 11a. The holder 11 is formed with plural communication holes 11d extending radially of the holder and having both ends thereof which are open to an outer peripheral face, formed with a thread 11c, of the holder and the recess 11a, respectively.
The test-piece holding member 12 is comprised of a tubular portion 12a mounted to the inner peripheral face of the holder 11 so as to close an opening face of the recess 11a on the radially inward side, and a flange portion 12c projecting from a central part of the inner peripheral face of the tubular portion 12a in the radially inward direction. A test-piece supporting hole 12b is formed in a central part of the flange portion 12c. As shown in FIG. 2, the test-piece holding member 12 is mounted to the inner peripheral face of the holder 11 through O-rings 13 fitted into the O-ring holding grooves 11b of the holder 11.
The mounting portion 1a, to which the test-piece supporting device 3 is mounted, of the cylindrical container 1 is formed with a suction hole 1b communicating with the communication hole 11d of the holder 11. By sucking, through the suction hole 1b, an air in the recess 11a whose opening face is closed by the tubular portion 12a of the test-piece holding member 12, part of the tubular portion 12a is pulled into the recess 11a and the flange portion 12c is elastically deformed, so that the diameter of the test-piece supporting hole 12b increases. In this condition, a cigarette C is inserted into the test-piece supporting hole 12b. Next, by stopping the suction of air in the recess 11a, the tubular portion 12a, the test-piece supporting hole 12b and the flange portion 12c of the test-piece holding member 12 are restored to their original shapes. As the diameter of the test-piece supporting hole 12b decreases, the cigarette C is supported at its outer peripheral face by the inner peripheral edge, defining the test-piece supporting hole 12b, of the flange portion 12c. At the same time, the flange portion 12c hermetically separates the internal space of the cylindrical container 1 into two spaces defined above and below the flange portion.
In a ventilation characteristic measurement with respect to a filter cigarette C, an amount Vf of air flowing into the second airtight chamber 2b and then entering into the cigarette through its filter plug section F and an amount Vp of air flowing into the third airtight chamber 2c and then entering into the cigarette through its shredded tobacco section T are measured, as the first airtight chamber 2a is evacuated at a predetermined flow rate Vc under a condition that the cigarette C is held in the cylindrical container 1 by means of the test-piece supporting devices 3a, 3b and 3c.
As shown in FIG. 5, a variety of types of cigarettes C is subject to the ventilation characteristic measurement, which are different for the entire cigarette length and for the filter section length. Thus, it is necessary to adjust the three holding positions at which a cigarette C is held by the first, second and third test-piece holding members 3a, 3b and 3c in accordance with the type of a cigarette to be measured, so as to hermetically separate the filter section F and the shredded tobacco section T from each other.
However, the three mounting portions 1a of the cylindrical container 1 are fixedly provided in the aforementioned conventional ventilation-characteristic measuring apparatus. This makes it very difficult to adjust the positions at which the test-piece supporting devices 3a, 3b and 3c are mounted to the cylindrical container 1. If, for example, the holder 11 is thickened, then the position at which the holder is threadedly engaged with the mounting portion 1a of the cylindrical container 1 becomes adjustable to some extent, but no sufficient width for adjustment of the three cigarette holding positions is provided because of constraints in increasing the thickness of the respective holder 11.
The aforesaid test-piece supporting device 3 which is threadedly mounted at its thread 11c to the mounting portion 1a of the cylindrical container 1 is disadvantageous in that much effort is required in mounting the same thereon and dismounting the same therefrom. In addition, the engagement face of the thread 11c at which the test-piece supporting device 3 is mounted on the cylindrical container 1 must be hermetically sealed, in order to control the diameter of the test-piece supporting hole 12b by sucking the air in the recess 11a through the communication hole 11d of the holder 11 and the suction hole 1b formed in the cylindrical container 1 in a condition that these holes are reliably communicated with each other. This necessitates a countermeasure such as the provision of a hermetic seal tape (not shown) for pipe-arrangement use. An operation of providing such a seal tape along the peripheral face of the thread 11c is burdensome. Moreover, the test-piece holding member 12, made of an elastic material such as rubber, entails a deterioration with a elapse of time and must be replaced. Upon replacement of test-piece holding members 12, the test-piece supporting device 3 must be dismounted from the cylindrical container 1. In this manner, the replacement of test-piece holding members 12 is burdensome.
Flow meters of a thermal type primarily employed in measuring air flow rates Vf and Vp are susceptible to affections of measurement circumstances (temperature and humidity), and must be prevented from being contaminated by an air containing dust and oil content. This requires a countermeasure such as a clean laboratory for the flow meters so as to guarantee the measurement accuracy of the flow meters.
Recently, a resistance type flow meter has been employed, and a pressure indicative of a flow rate is detected by means of a minute pressure-difference sensor (pressure sensor), to thereby measure the flow rate of air passing through the resistance type flow meter. However, the minute pressure-difference sensor is extremely high-priced although it is excellent in response characteristic.